Data analysis method for plasma processing apparatus, plasma processing method and plasma processing apparatus

ABSTRACT

A stable etching process is realized at an earlier stage by specifying the combination of wavelength and time interval, which exhibits a minimum prediction error of etching processing result within a short period. For this, the combination of wavelength and time interval is generated from wavelength band of plasma emission generated upon etching of the specimen, the prediction error upon prediction of etching process result is calculated with respect to each combination of wavelength and time interval, the wavelength combination is specified based on the calculated prediction error, the prediction error is further calculated by changing the time interval with respect to the specified wavelength combination, and the combination of wavelength and time interval, which exhibits the minimum value of calculated prediction error is selected as the wavelength and the time interval used for predicting the etching processing process.

BACKGROUND

The present invention relates to a method of analyzing data of a plasmaprocessing apparatus for processing a semiconductor wafer throughplasma, a plasma processing method, and a device used for the plasmaprocessing method.

In order to obtain the micro shape of the semiconductor device to beformed on the wafer, plasma processing such as an etching process isperformed for bringing a substance into an ionized state (plasma state)so as to remove the substance on the wafer through its action (reactionon the wafer surface).

The plasma processing apparatus such as the etching apparatus forprocessing with plasma is equipped with a spectroscope (OES: OpticalEmission Spectroscopy) which allows monitoring of the plasma light inorder to cope with light emission resulting from ionizing phenomenoncaused by the plasma. The data measured by the spectroscope will bereferred to as OES data.

In order to stabilize the micro shape of the semiconductor device, theetching apparatus is structured to apply control technology to measurethe OES data, predict etching processing results such as dimension ofthe micro shape, and adjust the etching processing condition.

It is necessary to predict the etching processing results with minimumerror by using the OES data for stabilization of the etching processingresult.

There is a known method of predicting the etching processing result asdisclosed in JP-4547396.

JP-4547396 discloses the method of predicting the etching processingresult by selecting monitor data and the corresponding time intervalwhich are used for predicting the etching processing result from monitordata of the apparatus, including the OES data, and predicting theetching processing result using values only of the selected monitor dataand the time interval, and the method of adjusting the etchingprocessing condition in accordance with the prediction result.

SUMMARY

JP-4547396 merely discloses the method of specifying the time intervalwith small prediction error of the etching processing result. The valueof the OES data varies depending on the wavelength of emitted light, andchanges over time during etching process. The prediction error maybecome large depending on combination of the selected wavelength andtime interval. In order to stabilize the etching processing result, itis necessary to specify the combination of the wavelength and the timeinterval, which exhibits the small prediction error of the etchingprocessing result. Because of a huge number of combinations ofwavelength and time interval, it is further necessary to specify thecombination with small prediction error from those combinations within ashort period in view of practical application for daily work.

An object of the invention is to provide a data analysis method of anetching apparatus, capable of executing the etching process stabilizedat an earlier stage by specifying both wavelength and time interval,which exhibit small prediction error of the etching processing resultwithin a short period, an etching method using the analysis result, andthe device used for the method.

The present invention provides a data analyzing method including thesteps of generating a combination of wavelength and time interval fromwavelength band of plasma emission generated by etching a specimen,calculating a prediction error upon prediction of an etching processingresult with respect to the generated combinations of wavelength and timeinterval, specifying the wavelength combination based on the calculatedprediction error to further calculate the prediction error by changingthe time interval with respect to the specified wavelength combination,and selecting the wavelength combination, which exhibits a minimum valueof the calculated prediction error, as the wavelength and the timeinterval used for predicting the etching processing result.

The present invention provides the etching method including the steps ofetching a specimen inside an exhausted vacuum processing chamber byintroducing etching gas into the chamber to generate plasma whilemonitoring emission of the generated plasma under a predeterminedetching processing condition, generating a wavelength combination fromwavelength band of plasma emission generated by etching the specimen,calculating a prediction error upon prediction of an etching processingresult with respect to the respectively generated wavelengthcombination, specifying the wavelength combination based on thecalculated prediction error, further calculating the prediction error bychanging the time interval with respect to the specified wavelengthcombination, selecting the combination of wavelength and time interval,which exhibits a minimum value of the calculated prediction error, asthe wavelength and the time interval used for predicting the etchingprocessing result, and adjusting the etching processing condition usinga prediction value of the etching processing result with respect to theselected wavelength and time interval.

The present invention provides an etching apparatus which includes aprocessing chamber, a plasma generating unit for generating plasma byintroducing etching gas into the processing chamber exhausted in vacuum,in which a specimen is disposed, an emission monitor unit for monitoringemission of the plasma generated by the plasma generating unit, anarithmetic unit for generating data concerning a condition ofcontrolling the plasma generating unit, a storage unit for storing thedata concerning condition of controlling the plasma generating unit,which has been generated by the arithmetic unit, and a control unit forcontrolling the plasma generating unit based on a state of the plasmaemission monitored by the plasma emission monitor unit and the controldata stored in the storage unit. The arithmetic unit generates awavelength combination from wavelength band of the plasma emission to begenerated by etching the specimen as a condition for etching thespecimen by the plasma generating unit, calculates a prediction errorfor prediction of the etching processing result with respect to thecombinations of wavelength and time interval, specifies a wavelengthcombination based on the calculated prediction error, further calculatesthe prediction error by changing the time interval with respect to thespecified wavelength combination, and selects the combination ofwavelength and time interval, which exhibits a minimum value of thefurther calculated prediction error, as the wavelength and the timeinterval used for prediction of the etching processing result so as togenerate the condition for etching the set specimen.

The present invention ensures to specify the combination of wavelengthand time interval, which only exhibits small prediction error of theetching processing result from the OES data, and to stabilize theetching processing result.

These features and advantages of the invention will be apparent from thefollowing more particular description of preferred embodiments of theinvention, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically representing a structure of anetching apparatus according to an embodiment of the invention;

FIG. 2 is a block diagram schematically representing a structure of anetching section of the etching apparatus according to the presentembodiment of the invention;

FIG. 3 is a graph representing an example of the OES data;

FIG. 4 shows a flowchart explaining an example of the control foradjusting the etching processing condition and a scatter chartrepresenting a relationship between the emission intensity monitorvalues and the etching processing result;

FIG. 5 is a table representing an example of etching processing resultdata according to an embodiment of the invention;

FIG. 6 is a table representing an example of OES data according to anembodiment of the invention;

FIG. 7 is a table representing an example of initial search result dataaccording to an embodiment of the invention;

FIG. 8 is a table representing an example of random number search resultdata according to an embodiment of the invention;

FIG. 9 is a table representing an example of final search result dataaccording to an embodiment of the invention;

FIG. 10A is a flowchart representing an analyzing process flow performedby an arithmetic unit according to an embodiment of the invention;

FIG. 10B is a flowchart representing the analyzing process flowperformed by the arithmetic unit according to the present embodiment ofthe invention, and specifically, details of step S202 of the flow shownin FIG. 10A;

FIG. 10C is a flowchart representing the analyzing process flowperformed by the arithmetic unit according to the present embodiment ofthe invention, and specifically, details of step S207 of the flow shownin FIG. 10B;

FIG. 10D is a flowchart representing the analyzing process flow executedby the arithmetic unit according to the present embodiment of theinvention, and specifically, details of step S207-1 of the flow shown inFIG. 10C;

FIG. 11 is a table of data representing emission intensity monitorvalues used for calculating a prediction error according to anembodiment of the invention;

FIG. 12 is a front view of a screen displaying a section for input ofwavelength for search and an analysis execution button according to anembodiment of the invention;

FIG. 13A is a scatter chart representing a relationship between theemission intensity monitor values and the etching processing results forexplaining the process of calculating the prediction error according toan embodiment of the invention;

FIG. 13B is a scatter chart representing a relationship between theemission intensity monitor values and the etching processing results forexplaining the process of calculating the prediction error according toan embodiment of the invention;

FIG. 14A is a scatter chart representing a relationship between theetching processing time and the emission intensity, indicating a timeseries change in the emission intensity according to an embodiment ofthe invention;

FIG. 14B is a scatter chart representing a relationship between theetching processing time and the emission intensity, indicating a timeseries change in the emission intensity according to an embodiment ofthe invention;

FIG. 15 is a front view of the screen displaying the initial searchresult according to an embodiment of the invention; and

FIG. 16 is a front view of the screen displaying the final search resultaccording to an embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The method of analyzing data of the etching apparatus according to theinvention allows acquisition of plasma emission data indicating theemission intensity with respect to a plurality of values of wavelengthand time, which are obtained upon the etching process and the etchingprocessing result, and evaluation of a prediction error of the etchingprocessing result based on the average value of the emission intensitywith respect to different combinations of wavelength and the timeinterval of the plasma emission data. This enables to specify thecombination of wavelength and time interval of the plasma emission dataused for prediction of the etching processing result based on theprediction error. This process is applied to the etching method and theetching apparatus. An embodiment of the invention will be describedreferring to the drawings. For all the drawings referred to explain thepresent embodiment, the same elements are designated with the samecodes, and repetitive explanations thereof, thus, will be omitted.

Etching Apparatus

As the structure of an etching apparatus according to the invention ofFIG. 1 indicates, an etching apparatus 1 includes an etching section 10,an analyzing section 20, an input section 30, an output section 31, anda communication interface section (communication IF section) 32, whichare mutually connected with one another via a bus 33.

The etching section 10 includes a plasma processing unit 11, aspectroscope (OES) 12, a control unit 13, and an interface unit (IFunit) 14. The plasma processing unit 11 generates plasma to process thewafer. The spectroscope (OES) 12 acquires the OES data as the plasmaemission data during the etching process. The OES data are stored in astorage unit 22 of the analyzing section 20 via the IF unit 14. Thecontrol unit 13 controls processing performed by the plasma processingunit 11. The etching section 10 will be described later in detailreferring to FIG. 2.

The analyzing section 20 executes the process of specifying thecombination of wavelength and time interval, which is used forprediction of the etching processing result. The analyzing section 20includes an arithmetic unit 21 for data analysis, the storage unit 22,and an interface unit (IF unit) 210.

The storage unit 22 includes an etching processing result data storageregion 23 for storing the etching processing result for each wafer, anOES data storage region 24 for storing measurement values of thespectroscope (OES) which are acquired during the etching process, aninitial search result data storage region 25 for storing initial searchresult data of the search process performed by the arithmetic unit 21, arandom number search result data storage region 26 for storing data of arandom search result performed by the arithmetic unit 21, a final searchresult data storage region 27 for storing final search result data, anda control condition data storage region 28 for storing conditions to becontrolled by the plasma processing unit 11 for etching process of thewafer.

The arithmetic unit 21 sequentially evaluates the prediction error forprediction of the etching result in accordance with the emissionintensity for each combination of wavelength and time interval in theetching processing result data storage region 23 of the storage unit 22,and the OES data stored in the OES data storage region 24. Then thearithmetic unit further specifies the combination of wavelength and timeinterval, which is used for prediction of the etching processing result.The analyzing process performed by the arithmetic unit 21 will bedescribed later in detail.

The input section 30 is formed as a mouse, a keyboard and the like forreceiving information input through operation of the user. The outputsection 31 is formed as a display, a printer and the like for outputtingthe information to the user. The communication IF section 32 is formedas an interface connected to another device (connectable to theinspection device for measuring etching processing results) and thesystem (connectable to the existing production management system) viathe bus 33, an external network and the like for receiving andtransmitting the information. The bus 33 serves to link the respectivesections (10, 20, 30, 31, 32). Each of the IF units (14, 210) in therespective sections is the interface for receiving and transmitting theinformation via the bus 33. The analyzing section 20 may be formed as anindependent analyzing device which is connected to the etching apparatusincluding the etching section 10 via the IF unit 210.

Etching Section

The etching section 10 includes the plasma processing unit 11, thespectroscope (OES) 12, the control unit 13, and the IF unit 14. Theplasma processing unit 11 includes a chamber 111 that is vacuumed by anot-shown vacuum exhaust unit, a pair of electrodes 112 a, 112 b whichgenerate plasma inside the vacuum exhausted chamber 111 in response toapplication of radio frequency power from a not-shown power source, awindow 115 which allows observation of the inside of the chamber 111from outside, and a gas supplier 117 in the vacuum exhausted chamber 111for supplying etching gas so as to subject the wafer 114 to the etchingprocess.

In the aforementioned structure, the plasma processing unit 11,according to an instruction from the control unit 13, generates plasmafrom the etching gas supplied from the gas supplier 117 through thenot-shown power source between the electrodes 112 a and 112 b to whichthe radio frequency power is applied in the state where the chamber 111that stores the wafer 114 is vacuum exhausted by the not-shown exhaustunit. The plasma gas 113 is impinged on the wafer 114 so as to beprocessed.

The thus generated plasma gas 113 includes an element contained in theetching gas supplied by the gas supplier 117 and an element generatedfrom the wafer 114 in processing, and emits a light ray 116 withwavelength in accordance with the element contained in the plasma gas113. The emitted light 116 is measured by the spectroscope (OES) 12through the window 115, and stored in the OES data storage region 24 ofthe storage unit 22 in the analyzing section 20 via the IF unit 14.

The control unit 13 serves to adjust an etching processing condition byinputting the OES data measured by the spectroscope (OES) 12 as theprocess of adjusting the etching processing condition to be describedlater in addition to an instruction given to the plasma processing unit11.

At the end of the etching process, the processed wafer 114 is taken fromthe chamber 111, and carried to another device (measurement device, forexample) so that another new wafer 114 is stored in the etching section10 for the etching process. The processed wafer 114 is subjected tomeasurement of a dimension of the pattern shape obtained as a result ofthe etching process performed by another device (measurement device).The dimension of the shape may be stored in the etching processingresult data storage region 23 of the storage unit 22 as the etchingprocessing result data.

OES Data

FIG. 3 shows a waveform signal 301 as an example of the OES data ofplasma emission measured by the spectroscope (OES) 12. The wavelengthband and intensity of the plasma emission will vary as passage of timeduring the etching process. The waveform signal 301 of the OES dataincludes two dimensional elements of wavelength and time, indicating thevalue of the emission intensity measured with respect to each waveformand each time. The value of the emission intensity measured for eachwaveform and each time will be stored in the OES data storage region 24to be described later together with the wafer ID having the OES datameasured.

Etching Processing Condition Adjustment Process

FIG. 4 shows an example of the etching processing condition adjustmentprocess performed by the control unit 13. The control unit 13 callscontrol data stored in the control condition data storage region 28 ofthe storage unit 22 in response to an instruction of an operator toadjust the etching processing condition (S101). The etching processingcondition adjustment process is sequentially performed for a pluralityof wafers using the control data stored in the control condition datastorage region 28. The first wafer is processed under the preliminarilyset condition.

The average value of the emission intensity of a predeterminedcombination of wavelength and time interval is calculated, or theaverage value of emission intensity of a predetermined combination ofwavelength and time interval is divided by the average value of emissionintensity of another predetermined combination of wavelength and timeinterval (S102). The value derived from dividing the average value ofthe emission intensity of the predetermined combination of wavelengthand time interval by the average value of emission intensity of anotherpredetermined combination of wavelength and time interval will behereinafter referred to as an emission intensity monitor value. Theaverage value of emission intensity of the predetermined combination ofwavelength and time interval may be set to the emission intensitymonitor value.

The control unit 13 predicts the etching processing result upon input ofthe aforementioned emission intensity monitor value (S103). A graph A101shows an example of the process of predicting the etching processingresult executed in S103. A y-axis and an x-axis of the graph A101represent the etching processing result and the emission intensitymonitor value, respectively. Each point A102 on the graph representseach sheet of the wafer. The graph shows the correlation between theemission intensity monitor value and the etching processing result. Astraight line A103 is a regression line indicating the relationshipbetween the emission intensity monitor value derived from a plurality ofpoints A102 and the etching processing result. The straight line A103 isdrawn so that the sum of squares of the distance from each point of aplurality of points A102 is minimized. In S103, the regression line A103is used to calculate a prediction value (pv) of the etching processingresult from the emission intensity (ei) as a dotted line shown in thedrawing.

The control unit 13 calculates the difference between a target value anda prediction value (pv) of the etching processing result (S104). Basedon the difference, the control unit calculates an adjustment value ofthe etching processing condition, for example, the flow rate of theetching gas (gas flow rate) supplied from the gas supplier 117, and timetaken for executing the etching process (S105).

The control unit 13 executes the etching process under the adjustedetching processing condition after completion of the process ofadjusting etching processing condition.

Analyzing Section

The information that specifies ID of the wafer subjected to the etchingprocess, and the information that specifies the etching processingresult will be stored in the etching processing result data storageregion 23 of the storage unit 22 shown in FIG. 1.

FIG. 5 shows an etching processing result data table 23 a as an exampleof the etching processing result data storage region 23. This tableincludes fields of columns 23 b for wafer ID and 23 c for etchingprocessing result.

The information that specifies the wafer 114 is stored in the column 23b for wafer ID. The value to be stored in the column 23 b for wafer IDis corresponded to the value stored in a column 25 b for wafer ID of anOES data table 25 a which will be described later so that the OES dataderived from etching the respective wafers are corresponded to theetching processing results.

The information that specifies the etching processing result is storedin the column 23 c for etching processing result. For example, themeasurement result of the surface shape of the wafer 114 specified inthe column 23 b for wafer ID (for example, dimension of the patternformed on the wafer 114 measured with a length measuring SEM, anddimension between patterns) which is measured after the etching processby using the measurement device which is connected to the etchingapparatus 1. The dimension information of the surface shape for eachwafer is stored in the etching processing result data storage region 23via the communication IF section 32.

FIG. 6 shows an OES data table 24 a as an example of the OES datastorage region 24. This table includes fields of columns 24 b for waferID, 24 c for wavelength, 24 d for time, and 24 e for emission intensity.The number of the tables corresponds to the number of wafers subjectedto the OES data measurement.

The column 24 b for wafer ID stores the information that specifies thewafer 114. The value stored in the column 24 b for wafer ID correspondsto the value to be stored in the column 23 b for wafer ID of the etchingprocessing result data table 23 a as described above.

The column 24 e for emission intensity stores the value of emissionintensity measured for each wavelength in the column 24 c forwavelength, and each time in the column 24 d for time, respectively.

FIG. 7 shows an initial search result data table 25 a as an example ofthe initial search result data storage region 25. This table includesvarious fields of columns 25 b for ID, 25 c for wavelength 1, 25 d forwavelength 2, 25 e for wavelength 1-time interval, 25 f for wavelength2-time interval, 25 g for prediction error, 25 h for prediction errorrank, 25 i for continuous search, 25 j for standard deviation ofemission intensity, 25 k for prediction error rank 1, and 25 l forprediction error rank 2.

Each field stores the information obtained through the analyzing processto be described later.

The column 25 b for ID stores the information that specifies thewavelength combination. The column 25 c for wavelength 1 stores theinformation that specifies a candidate of the wavelength used forprediction of the etching processing result. The value stored in a linei of the column 25 c for wavelength 1 will be referred to as WL1 forexplanation to be described later.

The column 25 d for wavelength 2 stores the information that specifies acandidate of the wavelength used for prediction of the etchingprocessing result. The value stored in a line i of the column 25 d forwavelength 2 will be referred to as WL2 for explanation to be describedlater.

The column 25 e for wavelength 1-time interval stores the informationthat specifies a candidate of the time interval used for prediction ofthe etching processing result. The value stored in a line i of thecolumn 25 e for wavelength 1-time interval will be referred to as WLT1for explanation to be described later.

The column 25 f for wavelength 2-time interval stores the informationthat specifies a candidate of the time interval to be used forprediction of the etching processing result. The value stored in a linei of the column 25 f for wavelength 2-time interval will be referred toas WLT2 for explanation to be described later.

Values stored in the columns 25 c for wavelength 1, 25 d for wavelength2, 25 e for wavelength 1-time interval, and 25 f for wavelength 2-timeinterval are used to predict the etching processing result in accordancewith the emission intensity monitor value derived from dividing theaverage value of the emission intensity in the time interval WLT1 storedin the column 24 d for time with respect to the wavelength WL1 stored inthe column 24 c for wavelength of the OES data table 24 a in the OESdata storage region 24 as shown in FIG. 6 by the average value of theemission intensity in the time interval WLT2 stored in the column 24 dfor time with respect to the wavelength WL2 stored in the column 24 cfor wavelength.

The column 25 g for prediction error stores the information thatspecifies the prediction error for predicting the etching processingresult using the calculated emission intensity monitor value inaccordance with values stored in the columns 25 c for wavelength 1, 25 dfor wavelength 2, 25 e for wavelength 1-time interval, and 25 f forwavelength 2-time interval.

The column 25 h for prediction error rank stores the value thatindicates the rank among information data stored in the respective linesof the column 25 g for prediction error. The column 25 i for continuoussearch stores the information that specifies the wavelength combinationfor continuous search in the time interval. The column 25 j for standarddeviation of emission intensity stores the information that specifiesthe standard deviation of the time series change in the emissionintensity.

The column 25 k for prediction error rank 1 stores the value indicatingthe rank of information data stored in the respective lines of thecolumn 25 g for prediction error. Such value is calculated with respectto the group (group of small standard deviation value) in the line,having the value stored in the column 25 j for standard deviation ofemission intensity smaller than a predetermined threshold value.

The column 25 l for prediction error rank 2 stores the value indicatingthe rank of information data stored in the respective lines of thecolumn 25 g for prediction error. Such value is calculated with respectto the group (group of large standard deviation value) in the line,having the value stored in the column 25 j for standard deviation ofemission intensity equal to or larger than the predetermined thresholdvalue.

FIG. 8 shows a random number search result data table 26 a as an exampleof the random number search result data storage region 26. This tableincludes fields of columns 26 b for ID, 26 c for wavelength 1, 26 d forwavelength 2, 26 e for wavelength 1-time interval, 26 f for wavelength2-time interval, 26 g for prediction error, 26 h for prediction errorrank, and 26 i for continuous search.

Each field stores the information obtained through the analyzing processto be described later.

The column 26 b for ID stores the information that specifies thewavelength combination common with the one stored in the column 25 b forID of the initial search result data table 25 a shown in FIG. 7. Thecolumn 26 c for wavelength 1 stores the information that specifies acandidate of the wavelength used for prediction of the etchingprocessing result. The column 26 d for wavelength 2 stores theinformation that specifies a candidate of the wavelength used forprediction of the etching processing result.

The column 26 e for wavelength 1-time interval stores the informationthat specifies a candidate of the time interval used for prediction ofthe etching processing result.

The column 26 f for wavelength 2-time interval stores the informationthat specifies a candidate of the time interval used for prediction ofthe etching processing result.

Like the initial search result data storage region 25 as describedabove, values stored in the columns 26 c for wavelength 1, 26 d forwavelength 2, 26 e for wavelength 1-time interval, and 26 f forwavelength 2-time interval represent each wavelength of emission andtime interval for predicting the etching processing result.

The column 26 g for prediction error stores the information thatspecifies the prediction error for predicting the etching processingresult using the emission intensity monitor value calculated with valuesstored in the columns 26 c for wavelength 1, 26 d for wavelength 2, 26 efor wavelength 1-time interval, and 26 f for wavelength 2-time interval.

The column 26 h for prediction error rank stores the value representingthe rank of information data stored in the respective lines of thecolumn 26 g for prediction error.

The column 26 i for continuous search stores the information thatspecifies the wavelength combination for continuous search in the timeinterval.

FIG. 9 shows a final search result data table 27 a as an example of thefinal search result data storage region 27. This table includes fieldsof columns 27 b for ID, 27 c for wavelength 1, 27 d for wavelength 2, 27e for wavelength 1-time interval, 27 f for wavelength 2-time interval,and 27 g for prediction error.

Each field stores the information obtained through the analyzing processto be described later.

The column 27 b for ID stores the information that specifies thewavelength combination common with the one stored in the column 25 b forID of the initial search result data table 25 a shown in FIG. 7. Thecolumn 27 c for wavelength 1 stores the information that specifies acandidate of the wavelength used for prediction of the etchingprocessing result. The column 27 d for wavelength 2 stores theinformation that specifies a candidate of the wavelength used forprediction of the etching processing result.

The column 27 e for wavelength 1-time interval stores the informationthat specifies a candidate of the time interval used for prediction ofthe etching processing result.

The column 27 f for wavelength 2-time interval stores the informationthat specifies a candidate of the time interval used for prediction ofthe etching processing result.

Like the explanation with respect to the initial search result datastorage region 25, values stored in the columns 27 c for wavelength 1,27 d for wavelength 2, 27 e for wavelength 1-time interval, and 27 f forwavelength 2-time interval represent the wavelength of emission and timeinterval of emission for predicting the etching processing result.

The column 27 g for prediction error stores the information thatspecifies the prediction error for predicting the etching processingresult using the emission intensity monitor value calculated with valuesstored in the columns 27 c for wavelength 1, 27 d for wavelength 2, 27 efor wavelength 1-time interval, and 27 f for wavelength 2-time interval.

Analyzing Process in Analyzing Section 20

The analyzing process according to the present embodiment is the methodof specifying the wavelength of plasma emission data and time which areused for prediction of the etching processing result in thesemiconductor etching process which etches the semiconductor wafer withplasma.

The method of analyzing process according to the present embodimentincludes six steps. In the first step, calculating a prediction errorupon prediction of the etching processing result using the emissionintensity average value in a first half of the time interval in theetching process as well as a prediction error used for the prediction ofthe etching processing result using the emission intensity average valuein a second half of the time interval in the etching process for eachcandidate of the wavelength used for prediction. In the second step,specifying a plurality of wavelength values each with small calculatedprediction error. In the third step, calculating the prediction error inpredicting an etching result by using an emission intensity averagevalue in the respectively set time intervals which are set by using therandom number for each of the specified plurality of wavelength valuesand. In the fourth step, specifying the wavelength value with smallprediction error calculated in the second evaluation step. In the fifthstep, calculating the prediction error in predicting an etchingprocessing result by using emission intensity average values for each ofall possible time intervals with respect to the specified wavelength.And in the sixth step, specifying a combination of wavelength and timeinterval, which is used for prediction of the etching processing result,by specifying the time interval with the minimum prediction error fromall possible time intervals with respect to the specified wavelength.

The specific method of analyzing process according to the presentembodiment will be described.

In a stage before sequentially etching a plurality of wafers using theetching apparatus 1 in the production process, an operator or a managerof the etching apparatus 1 executes the analyzing process through theanalyzing section 20 for determining the combination of wavelength andtime interval for prediction of the etching processing result.

Since the combination of wavelength and time interval suitable forprediction of the etching processing result varies depending on the filmstructure on the surface of the semiconductor wafer to be subjected bythe etching process, it is necessary to execute the analyzing process asneeded upon start of the etching process. Using the etching processingcondition determined by the aforementioned analyzing process, aplurality of wafer are sequentially subjected to the etching processthrough the etching apparatus 1 in the production process(mass-production process).

In execution of the analyzing process through the analyzing section 20,the condition for executing the analyzing process is input on a displayscreen 1200 as shown in FIG. 12. The operator inputs the wavelength forsearch in the column D101 for input of wavelength for search on thedisplay screen 1200, and clicks an analyzing execute button D102 toinstruct execution of analysis. The analyzing section 20 then performsthe analyzing process to output the combination of wavelength and timeinterval, which is suitable for prediction of the etching processingresult.

The column D101 for input of the wavelength for search on the displayscreen 1200 stores the information that specifies the wavelength forevaluating the prediction error. The predetermined wavelength(wavelength determined at an equal interval, for example, 201, 211) maybe automatically input in the column D101 for input of the wavelengthfor search. The wavelength indicating emission of an element containedin the plasma gas 113 may also be automatically input. The wavelengthhaving the emission intensity higher than that of the peripheralwavelength, that is, the wavelength indicating the plasma emission peakmay also be input in the column.

The analyzing process flow performed by the analyzing section 20 will bedescribed referring to FIGS. 10A to 10D.

The wavelength for search is input in the column D101 for input ofwavelength for search on the display screen 1200 shown in FIG. 12(S200). Then the combination of wavelength for search which has beeninput in S200 is generated, and stored in the initial search result datatable 25 a shown in FIG. 7 (S201). The prediction error in thedesignated time interval with respect to the combination of wavelengthfor search generated in S201 is calculated (S202). The standarddeviation of time series change in the plasma emission intensity iscalculated (S203). The wavelength combination is specified using theprediction error calculated in S202 and the standard deviationcalculated in S203 (S204). The initial search result is displayed on thescreen (S205).

It is determined whether or not the search is to be continued (S206). Ifthe search is not continued (No in S206), the process ends. Meanwhile,if the search is continued (Yes in S206), the time interval is searchedfor each wavelength combination using the random number to calculate theprediction error (S207). The wavelength combination is specified usingthe thus calculated prediction error (S208). The prediction error forall the patterns in the time interval is calculated with respect to thespecified wavelength combination (S209). The final search result isdisplayed (S210), and the process ends.

The respective process steps will be described in detail.

In S201, the arithmetic unit 21 generates a plurality of combinations oftwo wavelengths using a plurality of wavelengths for search which havebeen input in the column D101 for input of wavelength for search on thedisplay screen 1200 in S200 as shown in FIG. 12 so that each wavelengthof the combinations is stored in the columns 25 c for wavelength 1 and25 d for wavelength 2 of the initial search result data table 25 a,respectively as shown in FIG. 7. The combination to be stored may bethose of all the wavelengths input in the column D101 for input ofwavelength as shown in FIG. 12. The arithmetic unit 21 sequentiallyperforms numbering from the first line sequentially in the column 25 bfor ID as shown in FIG. 7.

In S202, the arithmetic unit 21 outputs the prediction error of theetching processing result derived from calculating the emissionintensity monitor value in the designated time interval with respect tothe wavelength combinations stored in the respective lines of theinitial search result data table 25 a shown in FIG. 7. The arithmeticunit 21 sequentially executes the process of the information from theupper line of the initial search result data table 25 a.

In this step specifically shown in FIG. 10B, the arithmetic unit 21performs the process of calculating the first prediction error using theemission intensity in the first half of the time interval in the etchingprocess (S202-1), and the process of calculating the second predictionerror using the emission intensity in the second half of the timeinterval in the etching process (S202-2). The minimum value of the firstand the second prediction error is stored in the corresponding line ofthe column 25 g for prediction error (S202-3). Then the time intervalthat provides the minimum value is stored in the columns 25 e forwavelength 1-time interval and 25 f for wavelength 2-time interval(S202-4).

The process of calculating the first prediction error in S202-1generates an emission intensity monitor value data table 29 a shown inFIG. 11 using the emission intensity value in the first half of the timeinterval in the etching process.

The column 29 b for wafer ID of the emission intensity monitor valuedata table 29 a stores the information that indicates the wafer withacquired data, for example, the information stored in the column 23 bfor wafer ID of the etching processing result table 23 a shown in FIG.5.

The column 29 c for emission intensity monitor value stores the emissionintensity monitor value obtained by dividing the first emissionintensity average value by the second emission intensity average value(S202-5) as shown below.

The first emission intensity average value is derived from values storedin the column 24 e for emission intensity of the OES data table 24 ashown in FIG. 6 at the row specified by the wavelength stored in thecorresponding line of the column 25 c for wavelength 1 of the initialsearch result data table 25 a shown in FIG. 7 in the time lines fromstart to the intermediate stage of the etching process. The time linesfrom start to the intermediate stage of the etching process correspondto those from 1 to 50 as shown in FIG. 6, for example.

The second emission intensity average value is derived from valuesstored in the column 24 e for emission intensity of the OES data table24 a shown in FIG. 6 at the row specified by the wavelength stored inthe corresponding line of the column 25 d for wavelength 2 of theinitial search result data table 25 a shown in FIG. 7 in the time linesfrom start to the end of the etching process. The time lines from startto the end of the etching process correspond to those from 1 to 100 asshown in FIG. 6, for example.

The column 29 d for etching processing result of the emission intensitymonitor value data table 29 a shown in FIG. 11 stores the value storedin the column 23 c for etching process result of the etching processingresult data table 23 a shown in FIG. 5 so as to be corresponded to thewafer ID (S202-6).

In the aforementioned step S202-1, the arithmetic unit 21 calculates theprediction error (e) upon prediction of the etching processing resultwith the emission intensity monitor value through the following formulae(1) to (5). The obtained prediction error (e) becomes the firstprediction error.

$\begin{matrix}{X_{11} = {{\Sigma \; x_{i}^{2}} - \frac{\left( {\Sigma \; x_{i}} \right)^{2}}{n}}} & \left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack \\{X_{12} = {{\Sigma \; y_{i}^{2}} - \frac{\left( {\Sigma \; y_{i}} \right)^{2}}{n}}} & \left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack \\{X_{13} = {{\Sigma \; x_{i}y_{i}} - \frac{\left( {\Sigma \; x_{i}} \right)\left( {\Sigma \; y_{i}} \right)}{n}}} & \left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack \\{a = \frac{X_{13}}{X_{11}}} & \left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack \\{e = \frac{\left( {X_{12} - {a\mspace{11mu} X_{13}}} \right)}{n}} & \left\lbrack {{Formula}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In the above formulae, the code x_(i) denotes the value stored at theith row of the column 29 c for emission intensity monitor value of theemission intensity monitor value data table 29 a shown in FIG. 11, andthe code y_(i) denotes the value stored at the ith row of the column 29d for etching processing result. The code n denotes the number of rowsof the emission intensity monitor value data table 29 a, and the code Edenotes the sum of all the rows of the emission intensity monitor valuedata table 29 a.

The calculated value will be described referring to FIGS. 13A and 13B. Agraph A200 shown in FIG. 13A and a graph B200 shown in FIG. 13B arescatter charts showing values stored in the column 29 c for emissionintensity monitor value and the column 29 d for etching processingresult.

The points, for example, a point A201 of the graph A200 shown in FIG.13A, and a point B201 of the graph B200 shown in FIG. 13B, representvalues stored in the respective rows of the column 29 c for emissionintensity monitor value of the emission intensity monitor value datatable 29 a shown in FIG. 11. They are derived from plotting by takingthe value stored in the column 29 c for emission intensity monitor asthe horizontal axis, and taking the value stored in the column 29 d foretching processing result as the vertical axis.

A straight line A202 of the graph A200 shown in FIG. 13A and a straightline B202 of the graph B200 shown in FIG. 13B represent straight lines(recession lines) which minimize the average value of sum of squares ofthe distance from each point. The first prediction error (e) calculatedthrough the formula 5 represents a square root of sum of squares of thedistance between each point and the straight line.

FIGS. 13A and 13B are scatter charts for taking the emission intensitymonitor values with respect to combinations of different values ofwavelength and time interval. Accordingly, values of the etchingprocessing results at the respective points are the same, but those ofthe emission intensity monitor are different.

Comparing the calculated prediction errors (e) between those shown inthe graph A200 of FIG. 13A and the graph B200 of FIG. 13B, theprediction error (e) of the graph A200 of FIG. 13A becomes smaller.Referring to the graph A200 of FIG. 13A, the points distribute closer tothe recession line comparing to the graph B200 of FIG. 13B, and itclearly shows that the emission intensity monitor values of FIG. 13A aremore suitable for prediction of the etching processing result in theaforementioned step of calculating the etching processing resultprediction value (S103). By selecting the wavelength and the timeinterval having smaller prediction error (e), it makes possible to setthe wavelength and the time interval which are suitable for the processof calculating prediction values of the etching processing result.

The calculated prediction error (e) is stored in the corresponding lineof the column 25 g for prediction error of the initial search resultdata table 25 a shown in FIG. 7 as the information for evaluatingadequacy of the combination of wavelength and time interval in thesubject line.

Any value other than the prediction error calculated herein may be usedso long as such value represents dispersion of the prediction resultupon prediction of the etching processing result using the emissionintensity monitor value. For example, it is possible to use thecorrelation coefficient or square of correlation coefficient between theemission intensity monitor value and the etching processing result.

In the process step S202-2 of calculating the second prediction error,like the process step of calculating the first prediction error, theemission intensity value in the second half of time interval in theetching process is used to generate the emission intensity monitor valuedata table 29 a shown in FIG. 11, and to calculate the prediction error(e) upon prediction of the etching processing result using the emissionintensity monitor value 29 c through the formulae 1 to 5. The resultantprediction error (e) becomes the second prediction error.

In calculation of the second prediction error, the column 29 c foremission intensity monitor value stores the emission intensity monitorvalue obtained by dividing the first emission intensity average value bythe second emission intensity average value as described below.

The first emission intensity average value is derived from values storedat the row specified by the wavelength stored in the corresponding lineof the column 25 c for wavelength 1 of the initial search result datatable 25 a shown in FIG. 7 in the time line from the intermediate stageto the end of the etching process in the column 24 e for emissionintensity of the OES data table 24 a of FIG. 6. For example, the timeline from the intermediate stage to the end of the etching processrepresents those from 51 to 100 in the column 24 d for time shown inFIG. 6.

The second emission intensity average value is derived from valuesstored at the row specified by the wavelength stored in thecorresponding line of the column 25 d for wavelength 2 in the time linefrom start to the end of the etching process in the column 24 e foremission intensity of the OES data table 24 a of FIG. 6. For example,the time line from start to the end of the etching process representsthose from 1 to 100 shown in FIG. 6.

In S202-3, the arithmetic unit 21 compares the first prediction errorcalculated in S202-1 with the second prediction error calculated inS202-2, and stores the minimum value in the corresponding line of thecolumn 25 g for prediction error shown in FIG. 7.

In S202-4, if the first prediction error is minimum, the arithmetic unitstores the information indicating the time interval from start to theintermediate stage of the etching process in the column 25 e forwavelength 1-time interval shown in FIG. 7, and further stores theinformation indicating the time interval from start to the end of theetching process in the column 25 f for wavelength 2-time interval.

If the second prediction error is minimum, the information indicatingthe time interval from the intermediate stage to the end of the etchingprocess is stored in the column 25 e for wavelength 1-time intervalshown in FIG. 7, and the information indicating the time interval fromstart to the end of the etching process is stored in the column 25 f forwavelength 2-time interval.

Since the element contained in plasma changes as the etching processproceeds, the plasma emission data will change depending on the firsthalf and the second half of the etching process. By evaluating theprediction error in a classified manner into the first half and thesecond half of the time interval, it makes possible to specify the timeinterval suitable for prediction of the etching processing result.

In the above method, the time interval of the emission intensity of thewavelength of the divided part is separated into the first half and thesecond half. It is also possible to calculate the prediction error byseparating the time interval into the first half and the second halfwith respect to the wavelength of the dividing part. The first half orthe second half of the time interval may further be divided in detail tocalculate the prediction error so as to use the resultant minimum value.

In S203, the arithmetic unit 21 calculates the standard deviation oftime series change in the emission intensity for the respectivecombinations of wavelength stored in the lines of the initial searchresult data table 25 a shown in FIG. 7, and the resultant value isstored in the column 25 j for standard deviation of emission intensity.The arithmetic unit 21 sequentially executes the process from the upperline of the initial search result data table 25 a. The line to beprocessed will be referred to as the subject line.

In the column 24 e for emission intensity of the OES data table 24 a inFIG. 6, the standard deviation of time series change in the emissionintensity is calculated through the formula 6 with respect to data atthe row specified by the wavelength stored in the subject line of thecolumn 25 c for wavelength 1 shown in FIG. 7.

$\begin{matrix}{{sd} = {\left\{ {{\Sigma \; z_{i}^{2}} - \frac{\left( {\Sigma \; z_{i}} \right)^{2}}{m}} \right\}/\left( {m - 1} \right)}} & \left\lbrack {{Formula}\mspace{14mu} 6} \right\rbrack\end{matrix}$

Referring to the formula 6, the code z_(i) denotes the value stored inthe ith line among those data pieces at the row specified by thewavelength stored in the subject line in the column 25 c for wavelength1 shown in FIG. 7. The code m denotes the number of lines of the column24 e for emission intensity. The code Σ denotes the sum of data in allthe lines of the column 24 e for emission intensity. The sd valuecalculated through the formula 6 is one of values indicating the degreeof time series change in the emission intensity.

FIGS. 14A and 14B show the respective time series changes in theemission intensity for each wavelength. A graph 1410 of FIG. 14A hassmall time series change in emission intensity 1411, and a small sdvalue. The wavelength of this type has small change in the average valueof the emission intensity even if the time interval is changed.Accordingly, changing the time interval is not likely to improve theprediction error.

Meanwhile, a graph 1420 of FIG. 14B has large time series change inemission intensity 1421 as well as a large sd value. The wavelength ofthis type has the average value of emission intensity which largelyvaries with change in the time interval. Accordingly, changing the timeinterval is likely to improve the prediction error. In the process ofspecifying the wavelength combination in S204, the wavelengthcombination is specified in consideration of the sd value.

The step S203 calculates the sd value with respect to the wavelengthstored in the column 25 c for wavelength 1 shown in FIG. 7. It is alsopossible to calculate the sd value with respect to the wavelength storedin the column 25 d for wavelength 2. It is further possible to obtainthe sum or a weighted average of the sd value calculated with respect tothe wavelength stored in the column 25 c for wavelength 1 and the sdvalue calculated with respect to the wavelength stored in the column 25d for wavelength 2 so as to be stored in the column 25 j for standarddeviation of emission intensity.

In S204, the arithmetic unit 21 determines the specified wavelengthcombination for continuous search in the time interval using the valuestored in the column 25 g for prediction error and the value stored inthe column 25 j for standard deviation of emission intensity.

The arithmetic unit 21 ranks the prediction error sequentially from thesmaller value in the line through calculation using the prediction errorvalue stored in the column 25 g for prediction error shown in FIG. 7,and stores the rank in the respective lines of the column 25 h forprediction error rank.

The arithmetic unit 21 ranks the prediction error sequentially from thesmaller value in the line through calculation with respect to the linein which the value stored in the column 25 j for standard deviation ofemission intensity is smaller than the predetermined threshold value 1(for example, 100), and stores the rank in the respective lines of thecolumn 25 k for prediction error rank 1. Likewise, the arithmetic unit21 ranks in the prediction error sequentially from the smaller value inthe line through calculation with respect to the line in which the valuestored in the column 25 j for standard deviation of emission intensityis equal to or larger than the threshold value 1, and stores the rank inthe respective lines of the column 25 l for prediction error rank 2.

The arithmetic unit 21 stores the code ◯ in the column 25 i forcontinuous search so that the search is continuously performed in thetime interval with respect to the line having the rank stored in thecolumn 25 h for prediction error rank, the column 25 k for predictionerror rank 1, or the column 25 l for prediction error rank 2 equal to orsmaller than a predetermined threshold value 2 (for example, 10). Thecode − is stored in the column 25 i for continuous search with respectto any other line.

The aforementioned process allows restriction of the wavelengthcombination for search in the time interval so as to reduce the searchtime.

In S205, the arithmetic unit 21 presents the information stored in theinitial search result data table 25 a to the operator so as to confirmwhether or not the continuous search is required.

FIG. 15 shows an example of a screen of the output displayed by thearithmetic unit 21 for the operator. An output screen 1500 shown in FIG.15 displays a list D200 of combinations of wavelength and time interval,a scatter chart display section D207, and a continuous searchinstruction section D208.

The list D200 of combinations of wavelength and time interval includescolumns D201 for prediction error rank, D202 for wavelength 1, D203 forwavelength 2, D204 for wavelength 1-time interval, D205 for wavelength2-time interval, and D206 for prediction error. Information data piecesrespectively stored in the columns 25 h for prediction error rank, 25 cfor wavelength 1, 25 d for wavelength 2, 25 e for wavelength 1-timeinterval, 25 f for wavelength 2-time interval, and 25 g for predictionerror of the initial search result data table 25 a shown in FIG. 7 aredisplayed from the first ranked line stored in the column 25 h forprediction error rank in descending order.

The scatter chart display section D207 displays a scatter chart 1510showing the emission intensity monitor values and the etching processingresults which are derived from calculating the emission intensitymonitor values with respect to combination of wavelength and timeinterval with first ranked prediction error.

The continuous search instruction section D208 displays the informationfor confirming the operator whether or not the continuous search isrequired. Pressing a button D209 or D210 allows the arithmetic unit 21to advance the process to the next process step S206.

In S206, in response to pressing the button D209, that is, Yes in thecontinuous search instruction section D208 by the operator, the processproceeds to the next step S207. Meanwhile, in response to pressing thebutton S210, that is, No, the first ranked data shown in FIG. 15 isstored in the control condition data storage unit 28 to end theanalyzing process.

In S207, the arithmetic unit 21 evaluates the prediction error in thetime interval divided in more detail than the case in step S202 withrespect to the wavelength combination that the code ◯ indicating thecontinuous search is stored in the column 25 i for continuous search ofthe initial search result data table 25 a shown in FIG. 7. The line tobe processed will be referred to as the subject line. The detailedprocess flow in this step will be described referring to FIG. 10C.

In this step, the process of calculating the prediction error with theemission intensity in the time interval which has been set using therandom number (S207-1) is executed R times as the predetermined numberof times (for example, 1000 times) (S207-2), the minimum value of thecalculated prediction error values is stored in the subject line of thecolumn 26 g for prediction error of the random number search result datatable 26 a shown in FIG. 8 (S207-3), and the time interval for providingthe minimum value is stored in the columns 26 e for wavelength 1-timeinterval and 26 f for wavelength 2-time interval (S207-4). Thecombination of the wavelength for search and its ID are stored in thecolumns 26 b for ID, 26 c for wavelength 1, and 26 d for wavelength 2(S207-5).

The arithmetic unit 21 repeats the process of calculating the predictionerror (S207-1) R times to obtain R prediction errors in the differenttime intervals. The detailed procedure in the process of calculating theprediction error (S207-1) will be described referring to FIG. 10D. Inthe process of calculating the prediction error (S207-1), the emissionintensity monitor value data table 29 a shown in FIG. 11 is generatedlike the process in S202 to calculate the prediction error value throughthe formulae 1 to 5.

The column 29 b for wafer ID of the emission intensity monitor valuedata table 29 a shown in FIG. 11 stores the information indicating thewafer with acquired data, for example, the information stored in thecolumn 23 b for wafer ID of the etching processing result table 23 ashown in FIG. 5.

The arithmetic unit 21 selects two points using the uniform randomnumber from those in the time interval (in the example shown in FIG. 6,from 1 to 100) in the column 24 d for time, which are stored in the OESdata table 24 a shown in FIG. 6 (S207-1-2). The small value and thelarge value of those of the selected time are set to TS1 and TE1,respectively (S207-1-3). The arithmetic unit 21 calculates the thirdemission intensity average value of those stored at the row specified bythe wavelength stored in the corresponding line of the column 25 c forwavelength 1 shown in FIG. 7 in the time line from TS1 to TE1 of thecolumn 24 e for emission intensity of the OES data table 24 a of FIG. 6(S207-1-4).

The arithmetic unit 21 selects two points using the uniform randomnumber of time stored in the OES data table 24 a (S207-1-5). The smallvalue and the large value among the selected time values are set to TS2and TE2, respectively (S207-1-6). The arithmetic unit 21 calculates thefourth emission intensity average value of those stored at the rowspecified by the wavelength stored in the corresponding line of thecolumn 25 d for wavelength 2 shown in FIG. 7 in the time line from TS2to TE2 of the column 24 c for emission intensity of the OES data table24 a of FIG. 6 (S207-1-7).

The column 29 c for emission intensity monitor value shown in FIG. 11stores the value obtained by dividing the third emission intensityaverage value by the fourth emission intensity average value (S207-1-8)as described below.

The column 29 d for etching processing result of the emission intensitymonitor value data table 29 a stores the value stored in the column 23 cfor etching processing result of the etching processing result table 23a shown in FIG. 5 so as to be corresponded to the wafer ID (S207-1-9).

The arithmetic unit 21 calculates the prediction error (e) forprediction of the etching processing result using the emission intensitymonitor value through the aforementioned formulae 1 to 5 (S207-1-10).The calculated prediction error (e) becomes the one to be obtained inS207.

The arithmetic unit 21 stores the minimum value of prediction errorscalculated R times in the subject line of the column 26 g for predictionerror of the random number search result data table 26 a shown in FIG. 8in S207-3, and stores the time interval providing the minimum value inthe columns 26 e for wavelength 1-time interval and 26 f for wavelength2-time interval in S207-4. The wavelength combination determined to besearched in S207-5 and the corresponding ID are stored in the columns 26b for ID, 26 c for wavelength 26 c, and 26 d for wavelength 2,respectively.

In S208, the arithmetic unit 21 calculates the rank of the predictionerror values from the line of smaller value so as to be stored in therespective lines of the column 26 h for prediction error rank using theprediction error value stored in the column 26 g for prediction error ofthe random search result data table 26 a shown in FIG. 8. The arithmeticunit 21 specifies the line with the lowest rank stored in the column 26h for prediction error rank, stores the code ◯ in the column 26 i forcontinuous search so that the search in the time interval is continuedin the subject line, and further stores the code − with respect to anyother line in the column 26 i for continuous search. In this example,only one line is specified. However, it is possible to specify aplurality of lines in the order of smaller prediction error with thecode ◯ for continuous search.

The aforementioned process makes it possible to restrict the wavelengthcombination for search in the time interval, thus reducing the searchtime.

In S209, the arithmetic unit 21 specifies the line that stores the code◯ indicating the continuous search in the column 26 i for continuoussearch of the random number search result data table 26 a shown in FIG.8, reads the information stored in the subject line of the columns 26 bfor ID, 26 c for wavelength 1 and 26 d for wavelength 2, and stores theread information in the columns 27 b for ID, 27 c for wavelength 1, and27 d for wavelength 2 of the final search result data table 27 a shownin FIG. 9.

The arithmetic unit 21 further calculates the emission intensity monitorvalue with respect to combination of all the possible time intervalswith the wavelength stored in the columns 27 c for wavelength 1 and 27 dfor wavelength 2, and calculates the prediction error (e) with respectto the emission intensity monitor values through the formulae 1 to 5.Among the calculated values of prediction error (e), the minimum valueis stored in the column 27 g for prediction error of the final searchresult data table 27 a, and the time interval providing the minimumvalue is stored in the columns 27 e for wavelength 1-time interval and27 f for wavelength 2-time interval.

If the code ◯ indicating the continuous search is stored in a pluralityof lines of the column 26 i for continuous search, the prediction error(e) is calculated with respect to the combinations of all possible timeintervals with the wavelength values in the respective lines. Amongcombinations of the respective wavelength values and time intervals, thecombination of wavelength and time interval, which exhibits the minimumprediction error, and the corresponding ID are stored in the finalsearch result data table 27 a.

In S210, the arithmetic unit 21 outputs the values stored in the finalsearch result data table 27 a shown in FIG. 9 and data relevant to thescatter chart on the screen as the final search results to end theprocess. FIG. 16 shows an example of the output screen presented by thearithmetic unit 21 to the operator.

The output screen shown in FIG. 16 displays a table D300 of combinationof wavelength and time interval, which exhibits the first rankedprediction error, and a scatter chart display section D307.

A column D301 for prediction error rank of the table D300 of wavelengthand time interval which exhibits the first ranked prediction errorstores the number 1 indicating that the value with the minimumprediction error among those of the searched wavelength and timeinterval. The columns D302 for wavelength 1, D303 for wavelength 2, D304for wavelength 1-time interval, D305 for wavelength 2-time interval, andD306 for prediction error are displayed so as to display informationstored in the columns 27 c for wavelength 1, 27 d for wavelength 2, 27 efor wavelength 1-time interval, 27 f for wavelength 2-time interval, and27 g for prediction error.

The scatter chart display section D307 displays the scatter chart 1610of the emission intensity monitor values and the etching processingresult upon calculation of the emission intensity monitor value withrespect to the combination of wavelength and time interval, whichexhibits the first ranked prediction error.

The operator is allowed to identify the combination of wavelength andtime interval which exhibits small prediction error of the etchingprocessing result by confirming the output screen shown in FIG. 16.

The content displayed on the output screen which has been stored in thefinal search result data table 27 a shown in FIG. 16 is stored in thecontrol condition data storage region 28 of the storage unit 22 shown inFIG. 1. In mass production, the data stored in the control conditiondata storage region 28 is used to control the plasma processing unit 11with the control unit 13 for sequentially etching the wafer 114.

As described above, use of the analyzing method performed by the etchingapparatus 1 (analyzing section 20) according to the present embodimentmakes it possible to easily identify the combination of wavelength andtime interval which exhibits the small prediction error of the etchingprocessing result, from a plurality of combinations of wavelength andtime interval.

The embodiment allows adequate determination of a plurality ofconditions of measurement wavelength and measurement time as the plasmaemission monitor condition. This makes it possible to execute theetching process highly accurately by maintaining the suitable flow rateof the etching processing gas.

The embodiment allows adequate determination of a plurality ofconditions of measurement wavelength and measurement time as the plasmaemission monitor condition. This makes it possible to provide theprediction value of the etching processing result with high accuracywhile reducing the error compared with the related art.

As a result, it is possible to calculate the difference between thetarget value and the prediction value of the etching processing resultwith higher accuracy. The etching process is executed while accuratelycontrolling the adjustment value of the etching processing condition,for example, the flow rate of the etching gas (gas flow rate) suppliedfrom the gas supplier 117 so as to ensure formation of the fine shapepattern in the stable state.

The present invention has been described based on the present embodimentin detail. However, it is to be understood that the invention is notlimited to the present embodiment as described above, and may bevariously modified so long as it does not deviate from the scope of theinvention.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims, rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

1-6. (canceled)
 7. An etching apparatus comprising: a processingchamber; a plasma generating unit for generating plasma by introducingetching gas into the processing chamber exhausted in vacuum, in which aspecimen is disposed; a plasma emission monitor unit for monitoringemission of the plasma generated by the plasma generating unit; anarithmetic unit for generating data concerning a condition ofcontrolling the plasma generating unit; a storage unit for storing thedata concerning a condition of controlling the plasma generating unit,which has been generated by the arithmetic unit; and a control unit forcontrolling the plasma generating unit based on a state of the plasmaemission monitored by the plasma emission monitor unit and the controldata stored in the storage unit, wherein the arithmetic unit generates awavelength combination from wavelength band of the plasma emission to begenerated upon etching of the specimen as a condition for etching thespecimen by the plasma generating unit, sets a time interval forcalculating an average value of emission intensity in a time period foretching the specimen with respect to the generated wavelengthcombination, calculates a prediction error for prediction of the etchingprocessing result using the average value of the emission intensity inthe time interval with respect to each of the generated wavelengthcombinations, specifies a combination of wavelength and time interval,which exhibits a minimum value of the calculated prediction error, andgenerates a condition for etching the specimen using a prediction valueof the etching processing result with respect to the combination ofwavelength and time interval, which exhibits the minimum value of thespecified prediction error.
 8. The etching apparatus according to claim7, wherein the arithmetic unit specifies the wavelength combination fromthe calculated prediction error, calculates a second prediction error bysearching the time interval with respect to the specified wavelengthcombination, and selects the combination of wavelength and timeinterval, which exhibits a minimum value of the second prediction error,as the wavelength and the time interval used for predicting the etchingprocessing result.
 9. The etching apparatus according to claim 7,further comprising an output section which outputs informationconcerning the combination of wavelength and time interval, whichexhibits the minimum value of the prediction error selected, as thewavelength and the time interval for predicting the etching processingresult by the arithmetic unit together with information of theprediction error.